Numerous polythiophenes have been studied extensively due to their interesting electrical and/or optical properties. Polythiophenes become electrically conducting upon chemical or electrochemical oxidation or reduction.
EP-A 339 340 discloses a polythiophene containing structural units of the formula:
in which A denotes an optionally substituted C1-4-alkylene radical and its preparation by oxidative polymerization of the corresponding thiophene.
EP-A 440 957 discloses dispersions of polythiophenes, constructed from structural units of formula (I):
in which R1 and R2 independently of one another represent hydrogen or a C1-4-alkyl group or together form an optionally substituted C1-4-alkylene residue, in the presence of polyanions.
The preparation of poly(fluorinated 3-alkylthiophenes) was first reported by Buchner et al. in 1990 in Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, volume 277, pages 355–358, who found that the strong inductive electron withdrawing effect of the perfluoroalkyl chain increased the oxidation potential of the thiophene ring compared to the non-fluorinated alkyl thiophene and the third-order optical nonlinearities in such polymers were reported by the same group in 1993 in Optical Engineering, volume 32, pages 2246–2254.
Zhang et al. in 1996 reported in the Chinese Journal of Organic Chemistry, volume 14, pages 330–337, the electrochemical polymerization of 3-fluoroalkoxy and 3-fluoroether thiophenes and in 1997 reported in the Chinese Journal of Organic Chemistry, volume 15, lines 15–23, that the introduction of a fluoroether functional group at the 3-position of the thiophene ring led to an increase in the oxidation potential of the monomer and to a decrease in the conductivity of the resulting polymers, even with the use of a methylene group as a spacer.
Over the period 1998 to 2002, Collard et al. have reported a number of studies concerning the synthesis and properties of semifluoroalkyl-substituted polythiophenes. In 1998 in Polymer Preprints, volume 39, pages 155–156, they reported the effect of perfluoroalkyl substituents on the surface properties and self-assembly of conjugated polymers; in 1999 in Macromolecules, volume 32, pages 4232–4239, they reported the synthesis of such polymers; in 2000 in Macromolecules, volume 33, pages 6916–6917, they reported controlling the macromolecular architecture of poly(3-alkylthiophene)s by alternating alkyl and fluoroalkyl substituents and in Macromolecules, volume 33, pages 3502–3504, they reported liquid crystalline regioregular semifluoroalkyl-substituted polythiophenes; and in 2002 in Polymeric Materials Science and Engineering, volume 86, pages 38–39, they reported that regioregular poly[3-alkylthiophene-alt-3-(semifluoroalkyl)-thiophene]s form highly-ordered solid-state lamellar structures with an interlayer spacing corresponding to a bilayer assembly. Furthermore, in 1998 Irvin and Reynolds in Polymers for Advanced Technologies, volume 9, pages 260–265, reported the synthesis, characterization and electrochemical polymerization of 1,4-bis[2-(3,4-ethylenedioxy)-thienyl]-2,5-difluorobenzene and 1,4-bis(2-thienyl)-2,5-difluorobenzene and the resultant polymers were found to be electroactive redox switchable films, with the more electron-rich ethylenedioxythiophene-derivative switching at lower potentials, and as thin films to exhibit electrochromic behaviour. However, no 3,4-alkylenedioxythiophenes [XDOT's] or polymers derived therefrom with direct substitution with fluorine atoms or alkyl groups substituted with a perfluoro-group have, to our knowledge, been reported in the literature.
There is a general requirement for new conductive polymers with unique combinations of optical and electrical properties.